Biology B1

Diet and Exercise

A person is malnourished if their diet is not balanced. This may lead to a person being overweight or underweight. An unbalanced diet may also lead to deficiency diseases or conditions such as Type 2 diabetes.

The metabolic rate varies with the amount of activity you do and the proportion of muscle to fat in your body. Metabolic rate may be affected by inherited factors

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Immune System

White blood cells help to defend against pathogens by:

■ ingesting pathogens

■ producing antibodies, which destroy particular bacteria or viruses

■ producing antitoxins, which counteract the toxins released by the pathogens.

it is difficult to develop drugs that kill viruses without also damaging the body’s tissues.

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Antibiotics

antibiotics kill individual pathogens of the non-resistant strain

■ individual resistant pathogens survive and reproduce, so the population of the resistant strain increases

■now, antibiotics are not used to treat non-serious infections, such as mild throat infections, so that the rate of development of resistant strains is slowed down.

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Uncontaminated culture

Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics.

For this:

■ Petri dishes and culture media must be sterilised before use to kill unwanted microorganisms

■ inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame.

■the lid of the Petri dish should be secured with adhesive tape to prevent microorganisms from the air contaminating the culture.

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Hormones / Menstrual cycle

Hormones are secreted by glands and are usually transported to their target organs by the bloodstream.

■follicle stimulating hormone (FSH) is secreted by the pituitary gland and causes eggs to mature in the ovaries. It also stimulates the ovaries to produce hormones including oestrogen.

■ oestrogen is secreted by the ovaries and inhibits the further production of FSH. It stimulates the production of LH.

■ luteinising hormone (LH) stimulates the release of eggs from the ovary

■ Progesterone maintains the lining of the uturus

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Auxin

Phototropism : When auxin is made at the shady part of a stem so the plant grows towards to light stimulus

Geotropism : When auxin helps a plant grow in response to the force of gravity

Upward growth ofplant shoots = negative geotropism

Downwards growth = positive geotropism

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Drugs

Drugs change the chemical processes in peoples’ bodies so that they may become dependent or addicted to the drug and suffer withdrawal symptoms without them

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Competition

Competition: limited to light, water, space and nutrients in plants;food, mates and territory in animals.

Extremophiles may be tolerant to high levels of salt, high temperatures or high pressures.

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Indicators

■ lichens can be used as air pollution indicators, particularly of the concentration of sulfur dioxide in the atmosphere

■invertebrate animals can be used as water pollution indicators and are used as indicators of the concentration of dissolved oxygen in water.

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Carbon Cycle

■ carbon dioxide is removed from the environment by green plants and algae for photosynthesis

■ when green plants and algae respire, some of this carbon becomes carbon dioxide and is released into the atmosphere

■ green plants and algae are eaten by animals and these animals are eaten by other animals

■ animals respire

■ when plants, algae and animals die, some animals and microorganisms feed on their bodies and carbon is released into the atmosphere as carbon dioxide when these organisms respire

■ combustion of wood and fossil fuels releases carbon dioxide into the atmosphere.

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Darwin's Theory

Darwin’s theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed more than three billion years ago.